I'm guessing a 4-6 weeks. But growth will depend on many factors: your location, sun exposure, temperature, humidity etc. Most moss (besides tropical moss like Spanish moss) will grow better in cool shaded areas. Water daily and do some research a particular moss that grow well in your area. Good luck :)

Hi Brittany !I wrote a blog post on the moss graffiti too. Doesn't it look FABULOUS ?! I can't wait to give it a try....although...I did write about some other ways to play with moss and get back at neighbours. haha. I couldn't help myself. I thought you may enjoy it too. Here is a link, if you wanted to read it ... http://www.lynneknowlton.com/2012/04/05/diy-green-moss-graffiti/